Guard band indicator



6, 1966 c. E. w. HOEBIS 3,266,722

' GUARD BAND INDICATOR Filed April 6, 1965 il 4 I- +jl w INVENTOR CHARLES E n. HOBB/S BY CGWHLAGENT Maw ATTORNEY United States Patent 3,266,722 GUARD BAND INDICATOR Charles E. W. Hobbis, Springfield, Va., assignor to the United States of America as represented by the Secretary of the Navy Filed Apr. 6, 1965, Ser. No. 446,127 7 Claims. (Cl. 235-70) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to calculators and more particularly to a guard band indicator wherein the mechanical distance between markers is fixed to prevent proximity of indications less than a predetermined minimum.

The trend today in military communication is toward broad band antennas multicoupled to a plurality of communication equipments. This trend is most noticeable on the larger Navy ships where communication ability and space are at a premium. One problem facing the operator of such equipment, is the need for calculating whether adjacent channels are beyond the guard band or minimum frequency separation required between channels on the same antenna for. proper signal isolation.

The general purpose of the present invention is to provide a simple precalculated indicator to designate not only the communication frequencies of the various channels fed into a single antenna, but also so constructed as to automatically prevent the possibility of channel separation less than the preascertained guard band.

It is accordingly an object of the present invention to provide a separation indicator where the degree of separation is a function of the mechanical construction of the indicator.

Another object is to provide an aid to communication equipment operators which warns of channel frequency separation requirements and eliminates the need for calculating these requirements.

A further object is to provide an indication of the signal frequencies of the communication channels multicoupled to an antenna while prohibiting indications not separated by a predetermined guard band.

Other objects and advantages of the invention will become more fully apparent and better understood from the following description of an embodiment of the invention selected by way of example, as illustrated in the accompanying drawings, in which:

FIG. 1 is an illustration ofa guard band indicator; and

FIG. 2 illustrates an example of a single cursor used with the indicator shown in FIG. 1.

Referring now to the drawings, wherein like reference characters designate like parts throughout, there is shown in FIG. 1 an indicia bearing member 41 graduated in a logarithmic scale extending from to 30 along the length thereof. The bounds of this scale can mark the bandwidth of an antenna, for example. As shown in this figure, the indicia bearing member, or fixed element of the slide rule has a groove 42 extending along the length of the top surface thereof, While it is noted that the bottom surface lacks such retaining means. Two cursors 43 are shown in FIG. 1 detachably secured in sliding contact with member 41. In FIG. 2 there is a more detailed showing of cursor 43. Each cursor is shown to have a tongue or key 44 serving to aid in the sliding movement of the cursor along the length of member 41. The tongue-in-groove coupling of the cursor with the member 41 prevents any skewing of the cursor about its vertical axis, thereby insuring greater accuracy of indication and freedom from binding during sliding. With only the top leg of a cursor having a slide Patented August 16, 1966 guide, it is possible to remove a cursor from the rule by lifting the cursor out and away from the bottom. Cursors can thus be detached and attached to the member 41 without disturbing the positioning of other cursors on this member. The member itself may have an upward canted bottom edge to insure the removability of the cursors. In addition, each cursor is equipped with a setscrew 46 enabling each of these indicators to be secured at a given position on the member. Also, centrally located in the back side of the face of each cursor is a marker or locator 45.

For a better understanding of the operation of the slide rule indicator of the present invention it will be noted that each of the cursors in FIG. 1 have a channel designation, the leftmost one being designated channel 1 and its adjacent counterpart being designated channel 2. Thus, each cursor represents a different one of the communication channels multicoupled into a single antenna. The minimum channel frequency separation necessary to maintain frequency isolation in most communication equipment presently used is ten percent of the signal. Given this percentage, the cursors are sized to a predetermined dimension so that the distance between any two markers of abutting cursors is the required ten percent separation. Thus, if a slide rule is to be used with the multicoupler of a particular antenna, the length of member 41, the spread of the logarithmic scale and the critical width dimension of the cursors are fixed parameters. Because of the logarithmic scale on the member 41 the width of the cursors, commensurate with a percentage, is the same for all cursors on a single slide rule. The physical dimension of the cursor is thus the feature of the present invention that commands the minimum channel separation required.

In FIG. 1, the cursor designated channel 1 indicates that the transmission frequency of this channel is 12 megacycles, the bandwidth of the antenna ranging from 10 to 30 megacycles, and that of channel 2 is 13.2 megacycles. Since these slidable members abut, their physical dimen sion prevents the separation between channels from being less than the ten percent required minimum separation. It is noted also that with channels 1 and 2 determined and set as shown in FIG. 1, additional channels may be tuned to any frequency between 10 and 10.8 megacycles and between 14.5 and 30 megacycles. The cursors thus mark the transmission of the frequency channels and also command the minimum guard band or frequency separation between channels.

It should be understood that between any two positions on the member 41 two values may be obtained in determining the guard band. For example, a ten percent guard band requirement for an equipment'operating at 12 megacycles is 13.2 megacycles on the high side. frequency separation down from 13.2 megaycles, however, is a diiferent value, 11.88 megacycles. As a general rule, each cursor would be sized from the larger operating fre quency as a conservative measure, although this procedure has not been followed in the example shown in drawlngs.

The practical utility of the calculator of the present invention is readily seen when the command to the operator is to tune a channel to 14 megacycles and the communication situation of the antenna is as shown in FIG. 1. When the operator attempts to place a cursor at 14 megacycles he is prohibited from doing so by the cursor at 13.2 megacycles and immediately is warned that the command cannot be carried out without violating the channel frequnecy separation on that particular antenna. The operator knows without making any calculations that another antenna must be used to obey the command.

The principles of the present invention have been shown A ten percent with reference to a particular slide rule. It is to be understood that the present invention is not limited to the structure of the instrument shown or heretofore described.

ments are encountered.

Nor is it necessary to limit the use of the present indicator to single antennas. Where antennas are in close proximity to each other, channel separation between equipments on the different antennas becomes a problem. Here, the indicators may be combined in an array with the cursors again providing guard band indication. The mechanical cursor buffeting action would be supplemented with other forms of indication, such as light sensing. Each cursor would be equipped to receive and transmit a warning signal when cursors representing channels on adjacent antennas came within the forbidden guard band. It should thus be understood that the principles of the present invention are intended to encompass different forms of slide rules as well as different cursor sensing means. So too, when equipments requiring only 5 percent frequency separation are included with percent limit apparatus, the indicator associated therewith would be adapted to represent these requirements.

Since various changes and modifications may be made in the practice of the invention herein described without departing from the spirit of scope thereof, it is intended that the foregoing description shall be taken primarily by way of illustration and not in limitation except as may be required by the appended claims,

What is claimed and desired to be secured by Letters 7 Patent of the United States is:

1. A minimum channel frequency separation indicator, comprising:

an indicia bearing member;

said indicia being arranged along the length of said -rnember in a logarithmic scale;

a plurality of cursors removably affixed to said indicia bearing member in slidable contact therewith along the length thereof;

each of said cursors having a designator thereon capable of alignment with said indicia;

said cursors being of fixed predetermined dimension along the length of said indicia bearing member such that when adjacent sides of any two of said cursors affixed to said indicia bearing member are caused to abut the distance between designators on said abutting cursors represents a minimum channel frequency separation.

2. A minimum channel frequency separation indicator as recited in claim 1, wherein each of said cursors represents a transmission channel and includes adjustable means to removably secure the cursors to said indicia bearing member at a selected indicium indicative of the transmission frequency of that channel represented.

3. A minimum channel frequency separation indicator as recited in claim 1, wherein said designators are located at the center of said cursors.

4. A minimum separation indicator as recited in claim 5 3, wherein said logarithmic scale is indicative of transmission frequency and each of said locator members represent one of the several communication channels multicoupled into a single antenna.

5. A minimum separation indicator as recited in claim 4, wherein said minimum separation commanded by the dimensions of said locator members along the length of said indicia bearing member is the frequency separation between channels required for signal isolation.

6. A minimum channel frequency separation indicator as recited in claim 3, wherein:

the spacing between said designators on said cursors is not less than ten percent of the channel frequency at which the cursor designators are positioned.

7. A minimum channel frequency separation indicator for multicoupled single antenna communication, coma prising:

a support member being graduated in a logarithmic scale indicative of transmission frequency;

a plurality of cursors detachably affixed to and slidably movable on said support member along the length thereof;

adjustable means for securing each of said cursors to said support member in any preselected position on said logarithmic scale provided the adjacent preselected positions have a spacing of at least a desired minimum frequency difference;

each of said cursors representing a different one of said channels and having marker means thereon to indicate the transmission frequency of the respective channels;

said cursors being so dimensioned along the length of said support member to prevent the difference between indications of abutting cursors from being less than said minimum channel frequency separation.

References Cited by the Examiner UNITED STATES PATENTS Smith.

Culligan 23589 12/1948 Chowns 23570.1

4/1958 Taylor 33-458 X FOREIGN PATENTS 12,935 5/1910 Great Britain. 962,836 7/1964 Great Britain.

Moses 3327 

